Performance of insulation materials for historic buildings: case-studies comparing super insulation materials and hemp-lime

There is a challenge to reduce the energy use of historic buildings while preserving their cultural values. New materials and solutions are being developed that could contribute to improving the energy performance of historic buildings without altering their character defining elements. The aim of this paper is to technically evaluate and compare a ‘high-tech’ material (VIP) with a ‘low-tech’ material (hemp-lime) for adding insulation to historical fa\ue7ades. This comparison was made with respect to thermal properties and moisture performance, as well as available environmental impact data. The VIPs are characterised by reaching a high level of insulation although they are thin, which means they do not alter the proportions of the building the way thick layers of insulation do. Hemp-lime on the other hand has the advantage of being in line with the traditional materials already present in historic buildings

Moisture fixation and thermal properties of lime–hemp concrete

Lime–hemp concrete (LHC) is a sustainable building material that combines hemp shiv and building limes. Moisture fixation and thermal properties of LHC were determined so as to gain knowledge about the material’s behaviour in a cold, wet climate. Sorption isotherms were produced over the whole moisture range for two LHC mixes by means of glass jar tests and a pressure plate apparatus. Thermal properties were determined for the mixes at different relative humidities using a transient plane source method. The results showed relatively low thermal conductivity and a steep sorption isotherm in the interval between 95% and 100% RH

Hampakalk : Tilläggsisolering på reveterade trähus och saltskadat tegelmurverk - Slutrapport

Historiska byggnaders energiprestanda behöver hållbart förbättras samtidigt som kulturhistoriska värden bevaras. Ett byggnadsmaterial som hampakalk skulle kunna uppfylla en ny funktion i renovering av historiska byggnader. Syftet var att finna en effektiv och resurssnål metod för tilläggsisolering av reveterade och putsade historiska trä- och tegelhus som är kompatibel med stommen, ökar energieffektiviteten, skapar en hälsosam och god inomhusmiljö samt bidrar till att bevarade kulturhistoriska värden. Målet med projektet var att utreda lämplighet och användbarhet av hampakalk som tilläggsisoleringsmaterial i ett kallt svenskt klimat med svåra fuktförhållanden. Det var väsentligt att klargöra förutsättningarna för eventuell mikrobiell påverkan på materialet. Ett delmål med projektet var därför att utvärdera risken för mikrobiell påväxt på hampakalk och att ta fram nyckeltal för dess kritiska fuktnivåer. Huruvida hampakalk skulle kunna fungera som tilläggsisolering på saltvittrande tegelmurverk har också undersökts. Här har det dels handlat om att förstå salternas beteende och skadeverkan samt vad som kan bidra till ett minimerande av skador. Där har hampakalk som invändigt tilläggsisoleringsmaterial provats och utvärderats för att se om det kan bidra med ändrat mikroklimat och ändrad salttransport och därigenom minskade saltskador på putsytan. Det finns ett stort bestånd av hållbara byggnader, företrädesvis från perioden 1700-tal till 1930-tal, som uppförts dels med trästomme som putsats, dels av tegel. Framförallt blev båda dessa byggtekniker allt vanligare under 1800-talet då städerna började byggas med ett utökat krav på brandskydd och termisk komfort. Idag är dessa byggnader ofta i behov av underhåll eller renovering och i samband med detta behöver de kunna anpassas efter moderna krav på termisk komfort och energieffektivisering. Samtidigt besitter de höga kulturhistoriska värden och skall därmed förändras/underhållas/renoveras med stor varsamhet, med traditionella material och metoder och med kompatibla lösningar. Resultatet av projektet har visat att hampakalk fungerar utmärkt för att tilläggsisolera historiska trä eller tegelbyggnader. Uppmätt minskning av energianvändning för uppvärmning var 33-53 % i fallstudierna jämfört med originalkonstruktionen. Tilläggsisolering av hampakalk gav en bra fuktbalans i såväl murverket som trästommen, förutsatt att det kombineras med en för konstruktionen anpassad kalkputs. Som invändig putsbärare på saltskadat tegelmurverk gav hampakalken ett stabilare mikroklimat med minskat antal saltkristallisationscykler och därmed ett fördröjt skadeförlopp. Hampakalk kan bidra till god ljudmiljö och ett bibehållet brandskydd. Hampakalk kan användas där kulturhistoriska värden skall bevaras. Det gäller framförallt byggnader som står inför renovering eller omrenovering, där ett material behövs som är kompatibelt med såväl trä- och tegelstommar som traditionell kalkputs vilka skall fortsätta utgöra kulturhistoriska värdebärande element för byggnaden

Moisture transport properties of lime-hemp concrete determined over the complete moisture range

To determine the durability of a lime-hemp concrete (LHC) wall and its resistance to driving rain, moisture conditions inside the wall have to be modelled. As model input, moisture transport properties were determined. Two LHC mixes were studied. Cup tests provided moisture diffusivity results at relative humidity (RH) values up to 95%. Capillary water uptake tests provided results for the interval 95-100% RH by means of curve fitting and the simulation tool JAM-KAP. A mix containing more lime showed higher moisture diffusivity at relative humidity >95%

Moisture Levels in Historic Timber Walls Insulated with Hemp-Lime

The European Union has a low-carbon roadmap that aims at reducing greenhouse gas emissions toprevent further climate change and achieve climate-neutrality by 2050. Many of the historical buildings that wehave today will still be around in 2050. Hence, there is a need to improve their energy performance. A way to dothis is to use hemp-lime as a material for renovation. Hemp shiv, the woody core parts of the hemp stem, can beused in combination with building limes to create a sustainable building material. Visby (a UNESCO World HeritageSite) is the capital of the Swedish island Gotland. It is dominated by historical timber houses with post-and-plankwalls. To improve air tightness and to reduce fire risks these timber houses were historically rendered with a thicklime render.The aim of this paper was to study moisture levels in two walls; one with a lime render and another with a hemplime render to determine the feasibility of using hemp-lime as an insulation material for retrofitting historic postand-plank walls. Two full-scale façades were constructed at Lund University, with a post-and-plank wall with athick lime render and a similar wall with a hemp-lime render. The façades had two different surface finishes: anair lime and a natural hydraulic lime, allowing for a comparison between the two. Moisture levels inside thefaçades were monitored for more than one year

Internal Retrofitting with Hemp-Lime on Brick Masonry : a Study to Prevent Damage Caused by Sodium Sulphate

In Sweden there are a great number of neo-gothic churches built in brick masonryaround 1870-1910. They are constructed as massive masonry walls with façadebricks attached to a core of massive red bricks. In the majority of these churchesthere is a presence of sodium sulphate causing salt damages. The source of the salts is known to be the red masonry bricks and the damage occurs both internally and externally on the walls. Damages occurred already after a couple of years after the churches were built and ever since they caused expensive renovations with little or no durability. As the sodium sulphate crystallizes inside the plaster the damages cause spalling of the surface.Since 2016 a method to prevent or delay salt damages has been studied and evaluated. By adding a layer of insulation on the internal wall the microclimate on and nearby the plaster surface can be changed and the damages caused by crystallization decrease. When adding an insulating layer made by hemp-lime plaster before adding the lime plaster the salts cause less visible damage to the internal plaster.Full-scale test surfaces have been made both in the laboratory and inside twochurches. After two and three years respectively, there are no visible salts causingdamages inside the churches, where salts previously came back directly after eachrenovation. In the wall in the laboratory at Lund University the bricks where contaminated with sodium sulphate and internally rendered with hemp-lime plaster with a lime plaster surface finish. Even though there are lots of salt-related damages externally there are thus far, more than two years after construction, no signs of any damage internally

Moisture Buffering of Hemp-Lime with Biochar and Rape Straw-Lime as Surface Materials for a Stable Indoor Climate

An appropriate and stable indoor climate in museums is crucial to guarantee an appropriate preservation of our cultural heritage. Depending on the collection, indoor temperature and relative humidity need to be kept within a certain range. Fluctuations in temperature and relative humidity could cause damage to museum artefacts and may require higher energy needs than necessary. Biochar is a material of which the use is relatively new in building materials. Previous studies have shown that biochar has unique moisture properties with a high surface area, high porosity and therefore high capability of moisture uptake. In Southern Sweden there are several biochar manufacturers that produce biochar from local biomasses such as seaweed, gardening wastes and residues from greenhouses.The aim of this project was to investigate the impact of hygroscopic surface materials on the indoor climate of buildings, focusing on moisture buffering and hygrothermal properties. The building materials that were studied were hemp-lime (with and without biochar) and rape straw-lime. Passively influencing the indoor climate by choosing appropriate surface materials could contribute to lower energy needs and less need for mechanical ventilation in historic buildings and museums without the need for excessive HVAC solutions

Understanding Deterioration due to Salt and Ice Crystallization in Scandinavian Massive Brick Masonry

Extensive durability problems such as weathering and degradation are found in historic Scandinavian brick masonry buildings, especially from the neo-Gothic period. These are largely due to the crystallization of salts and frost action in the bricks and mortars. This article aims to show and illustrate which salts and crystals are found in historic brick masonry buildings and to describe their appearance and behavior. An additional aim is to explore possibilities of preventing salt-related damage on internal masonry wall surfaces, such as using hemp-lime sacrificial plaster beneath the plaster. The objective is to show the mechanisms behind salt-related problems and to perform a case study and a laboratory study on salt-damaged brick masonry containing sodium sulphate. In order to prevent and stop damage to the masonry, it is important to be able to identify the nature of the salt damage and the type of salt that caused the damage. Neo-Gothic brick masonry buildings require well-planned, continuous maintenance of the masonry. It is therefore of the utmost importance to have an understanding of the complex functions of the masonry and of the salts that can cause damage to these historic buildings

Hållbar energieffektivisering av historiska trä- och stenbyggnader med hampakalk

Många historiska byggnader har de senaste decennierna tilläggsisolerats med moderna isoleringsmaterial som mineralull och cellplast. Att tilläggsisolera historiska byggnader kan leda till skador som orsakas av fukt och mögel, och utformningen av tilläggsisoleringen kan även leda till att kulturhistoriska värden går förlorade. Därför studeras ett nytt hållbart byggnadsmaterial, hampa-kalk, som tilläggsisoleringsmaterial för historiska byggnader. Fokus ligger på byggnadsbeståndet i Visby innerstad, med sina reveterade bulhus